The invention is directed to the use of nickel alloys for eyeglass (spectacle) frames and spectacle parts.
Eyeglass frames and eyeglass parts are frequently made of metals or metal alloys. Thereby, there are chiefly used copper alloys, such as, e.g., tin bronze (CuSn 6, CuSn 8), copper-bronze (Cu82 Ni2 Sn5 Zn 11) and new silver or nickel alloys which are distinguished by good workability, but have a high susceptibility to corrosion so that the eyeglass parts made of these materials must be provided with coatings made of more noble metals or alloys. The use of such compound materials, however, is unsatisfactory since even the smallest pores in the coatings permit corrosion of the supporting materials and glasses in use are subjected to an abrasive wear which after some time exposes the non-noble support material.
In recent times, there have been proposed for spectacle parts nickel--chromium and nickel-chromium-silver alloys (German OS No. 3045334) which we distinguished by good resistance to corrosion, but have a dificient workability. Thus, e.g., a nickel alloy having 10 to 15 percent chromium is only poorly workable by machining since it is inclined to weld to the tool. Indeed, the machining workability can be improved by the addition of about 1 percent of silver to the nickel-chromium but this is purchased as the expense of a higher material cost and a difficult working technique. The shaping of these materials without machining also is difficult since both types of materials (Ni-Cr, Ni-Cr-Ag) have a very steep hardening characteristic with increasing degree of mechanical working and so must be repeatedly soft annealed. Besides the mechanical working only succeeds with special rolls and special draw nozzles.
Therefore, it was the problem of the present invention to develop nickel alloys for eyeglass frames and eyeglass parts which are resistant to corrosion and nevertheless are readily formable and workable.